<div id="app"></div>

<script src="https://unpkg.com/@vue/reactivity@3.0.5/dist/reactivity.global.js"></script>
<script>

const { effect, ref } = VueReactivity

function renderer(domString, container) {
  container.innerHTML = domString
}

const count = ref(1)

effect(() => {
  renderer(`<h1>${count.value}</h1>`, document.getElementById('app'))
})

count.value++



</script>